Energy Consumption Of HVAC System Research Articles

Design and testing of a novel 3-fluid liquid-to-air membrane energy exchanger (3-fluid LAMEE)

Liquid-to-air-membrane energy exchangers (LAMEEs) are constructed with micro-porous semi-permeable membranes and transfer heat and water vapor between two separate fluids (air and liquid desiccant). Over the last decade, research has shown that LAMEEs can significantly reduce the energy consumption of HVAC systems. In this paper, a novel 3-fluid LAMEE prototype is designed and tested. The main objective of the proposed 3-fluid LAMEE is to enhance the performance (i.e. sensible, latent, and total effectivenesses, moisture removal rate, and sensible cooling capacity) of regular 2-fluid LAMEEs. The major difference between the proposed 3-fluid LAMEE and a 2-fluid flat-plate LAMEE is that, refrigeration tubes are placed inside the desiccant solution channels to enhance the cooling capacity and control the temperature of the desiccant solution along the length of the 3-fluid LAMEE. Water is used as the refrigerant in the current work. The main contribution of this paper is that it shows that the inlet temperature and mass flow rate of the cooling water have significant influences on the steady-state performance of the 3-fluid LAMEE. Compared to a 2-fluid LAMEE with the same design parameters, the sensible, latent, and total effectivenesses, moisture removal rate, and sensible cooling capacity of the 3-fluid LAMEE are improved by up to 69%, 28%, 39%, 54%, and 140% respectively, depending on the inlet temperature and mass flow rate of the cooling water.

Energy and visual performance of the silica aerogel glazing system in commercial buildings of Hong Kong

To achieve a more comfortable indoor environment while still retaining low energy consumption level is an exciting challenge for designers and owners of buildings. In this paper, a silica-aerogel filled super-insulating glazing system was proposed. A numerical study was conducted to analyze the energy performance and visual performance of the proposed glazing system. Two popular building simulation programs namely EnergyPlus and Radiance were applied in the numerical study. In the study of the energy performance, three control strategies (space temperature control, operative temperature control and PMV control) were applied to simulate the occupant’s control behavior toward the air-conditioning system in reality. The result indicated that compared with conventional single clear glazing, the silica aerogel glazing could retain a 4% longer thermally comfort period, while the energy consumption of HVAC system was reduced by 4–7%. The performance of the silica aerogel glazing was almost equal to that of the state-of-art low-e glazing. It is also concluded that as the occupant’s request on thermal comfort got stricter, the performance of the silica aerogel glazing would became better. In the visual comfort point of view, it can be concluded that the glare effect and near-window bright zone could be reduced significantly while indoor illumination level still met the requirement.

EnergyPlus and CHAMPS-Multizone co-simulation for energy and indoor air quality analysis

This paper presents a co-simulation method using EnergyPlus and CHAMPS-Multizone for combined energy efficiency and indoor air quality (IAQ) analysis. The energy simulation estimates the energy consumption of HVAC systems, lights, and electrical equipment. The Indoor Environmental Quality (IEQ) simulation predicts the indoor contaminate concentrations for IAQ, the zone air temperature and relative humidity for controlled zone conditions, the Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) for thermal comfort, and the illumination for daylighting performance. The energy, thermal comfort, and daylighting simulation are performed by EnergyPlus while the CHAMPS-Multizone is used for the IAQ simulation. In each time step, the CHAMPS-Multizone simulates the pollutant balance, and the ventilation rate required to control the contaminant concentrations under pre-established threshold values. EnergyPlus uses the ventilation rate to simulate the heat, air, and moisture balance, and the energy and daylighting performance. The Building Controls Virtual Test Bed is used for the run-time data exchange. Simulation cases using a 3-zone building are used to validate and demonstrate the benefit of the method. The co-simulation model is developed and implemented in a Virtual Design Studio (VDS) software framework with graphical user interface for integrated building system design. The co-simulation method is found to be especially useful in analyzing the interaction between IAQ and energy efficiency measures.

Energy Modeling and Chillers Sizing of HVAC System for a Hotel Building

With energy shortage issue rises, value of energy conservation grows. The energy consumption of HVAC system reaches about 50% of the building especially for the hot and humid ambient condition in Taiwan. Energy modeling code eQUEST was applied to evaluate the energy consumption of a hotel building. Through the validation of simulation data and field measurement data, the energy-efficient chiller sizing approach can be obtained. The results revealed that the energy saving of 10.5% can be achieved by optimizing the chiller capacity sizing. The approach by energy modelling in this study will identify the best practice under limited budget as well as to reduce the trial-and-error effort while chiller sizing decision for energy saving have to be carried out.

Prospects of green roof technology for energy and thermal benefits in buildings: Case of Jordan

Heat transfer has a substantial impact on thermal comfort for indoor architectural spaces, which is mainly dependent on building envelopes. Improving the quality of indoor spaces means applying a climate-conscious design that is very beneficial in decreasing energy consumption in buildings.In this paper, a study based on thermal calculations and computer simulation is conducted to demonstrate the thermal benefits on energy saving as an approach to increase energy efficiency through green roof technology. The study focuses on roof surfaces as they account for a large portion of the insulation impact on built environments. A comparison between regular roof and green roof technologies was conducted to explore the effect of green roof materials on thermal transmittance and eventually on energy consumption of HVAC systems in buildings.

탄소저감을 위한 3D BIM 기반 건물 에너지 효율화 방안

본 논문에서는 건물 내 HVAC시스템의 소비에너지 효율화를 목표로 한다. 이를 위해 건물 에너지 시뮬레이션과 유전알고리즘을 이용하여 HVAC시스템 내 급기 온도에 대한 제어 스케줄을 도출하였다. 연구 대상 건물은 90년대에 지어져 BIM이 구축되어 있지 않아 대성건물의 BIM을 구축하였고, 그 정보를 에너지 시뮬레이션 프로그램에 입력하여, 대상건물에 대한 에너지 시뮬레이션 모델을 구축하였다. 또한 실측한 소비에너지양 정보와 비교하여 대상건물 에너지 시뮬레이션을 실제 에너지 소비량 유사하게 보정하였다. 수정된 건물 에너지 시뮬레이션 모델과 유전자 알고리즘을 이용하여 에너지 효율화 급기 온도 스케줄이 작성되었다. 대상 건물에 적용되었을 때 에너지 절감 효과는 3%로 나타났다. 아직 이 분야는 설비의 제어 기법에 관한 연구가 미진하고, 주로 관리자의 경험을 통해 관리되는 측면이 있어, 에너지 시뮬레이션 프로그램에 의한 기법 개발 및 그에 대한 효과의 검증을 토대로 에너지 절감 기법에 대한 연구 및 개발이 필요하다. 본 연구는 HVAC system 제어 기법에 시발점이 될 것이다. This study deals with the BIM (Building Information Modeling)-based energy performance analysis implemented in EnergyPlus. The BIM model constructed at Revit is updated at Design Builder, adding HVAC models and converted compatibly with the EnergyPlus. We can obtain the input values about HVAC system and building environment such as HVAC system efficient, the number of air changes and energy consumption of equipment on applying GAs (Genetic algorithms). After modification about HVAC system, Optimization about HVAC system energy consumption can be analyzed. In order to maximize the building energy performance, a genetic algorithm (GA)-based optimization technique is applied to the modified HVAC models. Throughout the proposed building energy simulation, finally, the best optimized HVAC control schedule for the target building can be obtained in the form of "supply air temperature schedule". Throughout the supply air temperature schedule is applied to energy performance simulation, we obtained energy saving effect result on simulation.

Weather data generator to study climate change on buildings

Most computer programs that analyse the yearly performance of buildings require an input of historical series of weather data measured at the location of interest. However, analyses of climate change scenarios needs hourly weather data series that allow realistic changes in various weather parameters. This can not be done easily with the reference years based on measured weather data normally used. In this paper a weather generator is proposed in which climate changes can be implemented. Based on weather data observed over years a stochastic weather model is developed. This model is used to make a general model independent of the location and with which climate changes can be simulated. The general model can be adapted to a local climate change. Only new averaged values of the weather variables being the result of a climate change should be used as input. The model is able to generate hourly weather data that can be used as input for all kind of simulation programs to study the effect of climate change on the design and energy consumption of HVAC systems.

Simulation of the full and part load energy consumption of HVAC system of building

A model based on dynamic heat transfers through the building envelope and between the contents inside the building is developed. This model has been incorporated into the Computer Aided Building Airconditioning Requirement and Environmental Temperature Simulation (CABARETS) program. The model takes into account the interaction between the external excitation, building envelope, contents inside the building, air handling systems and the mechanical equipment. An iterative numerical procedure has been implemented to solve the simultaneous heat transfer equations for the various components of the system. The indoor temperature and humidity variations with or without the operation of the HVAC system are established, and the energy requirements for maintaining the controlled environment are computed. The electrical power requirement for operating the HVAC mechanical equipment is estimated by the model, and the values are compared with the observed electricity consumption for the mechanical services.